CSA advice,don't involve them they are useless,even my ex is wishing we didn't contact them.
To answer your question all that is taken into account,in my case,was my earnings they could'nt give two hoots about my outgoings.that was my personal financial arrangments with a third party.
It was based purely on my salary.
Considering just prior we had signed an agreement,drawn up by solicitor,that i would pay an agreed amount it was not long before she moved the goal posts when here living arrangements changed and she required more money as she would not be selling what was our property and moving in rent free with her wealthy fella.
TBH all that matters is that the children are not going without,i know that the money she recieves goes elswhere.
What is also forgotten is the fact that i still pay for my childs needs out of what i have left over when he is with me,he still needs clothes,schooling (private), food and days out when he is with me.
Trust me he does not go without.
One thing that i found slightly amusing was after she went to the CSA and renaged on our agreement she got and extra £4.99 a month,it was not worth the hassle,took the CSA just under 6 months to get it right.